Refining mineral lubricating oils



P 1938- J. M. PAGE, JR 2,129,282

REFINING MINERAL LUBRICATING OILS I Filed Feb. 17, 1936 8 F? I g grill,s g Q) gtjg" I h Y w {)2 z I a E 7 1 2 A g 8 g g g 1 N v a 0 :2, K R aVie Z ff INVENTO James Morris DagQ BY B JQ DMMW ATTORNEY Patented Sept.6, 1938 PATENT OFFICE 2,129,282 marmmc MINERAL LUBRICATING on.s

James Morris Page, In,

Casper, Wyo., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application February 1'1, 1936, Serial No. 64,217

5 Claims.

This invention relates to a process of refining mineral oils andspecifically petroleum lubricating oils of the type employed in thelubrication of internal combustion engines and commonly known as motoroils. The invention further relates to a process of extracting such oilswith a specific solvent, namely, beta beta dichlor diethyl ether,hereinafter referred to as chlor-ether." The use of this solvent for theextraction of mineral lubricating oils has been previously described inUnited States Patent. No. 2,003,238, entitled Process of separatingmineral oils" by H. T. Bennett, filed June 23, 1933.

More particularly, the present invention relates to an improvement inthe use of beta beta dichlor diethyl ether in lubricating oil extractionprocesses wherein undesirable naphthenic constituents are removed fromthe parafiinic com*- ponent of the oil. One object of the invention isto facilitate the use of said chlor-ether solvent in the extraction ofwax-containing lubrieating oil stocks. Another object of the inventionis to increase the selective solvent action of said solvent by theaddition of minor amounts of certain modifying agents. In the extractionof midcontinent and Salt Creek lubricating uistillates such as motor oildistillates falling within the viscosity range of 20 S. A. E. number,difiiculty has frequently been encountered with separation of wax in theextraction process. Where the distillate contains over 5% of paraflinwax and frequently as much as 10 or 15% thereof, the wax will usuallycrystallize in the form of a thick mush or magma at ordinarytemperatures and even at temperatures in the range of 100425 F. This isespecially true of the heavier distillates which contain higher meltingwaxes.

When extracting such wax-containing oils with beta beta dichlor diethylether it is usually necessary to maintain the temperature of the oilundergoing extraction below F. in order to obtain a satisfactory yieldof refined lubricating oil,

or raflinate, having the desired viscosity index.'

It is, accordingly, not feasible to carry out the extraction process ata temperature sufllciently high to maintain the wax in liquid form.

I have now discovered that the extraction of mineral lubricating oilswith chlor-ether is greatly improved by incorporating in the chlOr-ethera small amount, usually from2 to 20%, but possibly as much as 30%, orpropylene glycol. I have found that propylene glycol is miscible withchlorether to a very considerable extent as shown by the following tablewhich indicates the solubility Propylene glycol in mixture,

' Temperature percent The lowering of the miscibility temperature atconcentrations of propylene glycol in excess of about 16% is due to thereduction in the proportion of water in the mixture.

I have also found that the miscibility temperature of mineral oil andchlor-ether is very materially raised by the addition of propyleneglycol. The following table shows the effect on the miscibilitytemperature of chlor-ether and a cylinder stock derived from Salt Creekcrude. Three ratios of solvent to oil are given, and temperatures ofcomplete miscibility of oil and solvent are given with and without theaddition of 13% by volume of propyleneglycol to the chlor-ether.

By using propylene glycol to modify the-solvent action of chlor-ether inthis manner I am enabled to carry out my refining operation attemperatures ranging from to 200 F. The propylene glycol prevents thechlor-ether from dissolving, at these relatively high temperatures,excessive amounts of those hydrocarbons which are desired in therafilnate, yet it does not prevent the solution of naphthenicconstituents of the oil in the solvent.

As an example of the use of my new modified chlor-ether solvent, twovolumes of pure chlorether to one volume of Salt Creek cylinder stockwere used in an extraction carried out at -F. A yield of rafiinite oilof 58.2% was obtained, the oil having a viscosity index of 88. Incomparison with this two volumes of chlor-ether solvent containing 13%,by volume, of propylene glycol was applied to one volume or the same oilat the same temperature and a yield of 80% of raffinate oil wasobtained, the oil having a viscosity index of 85.2, only slightly lowerthan the viscosity index obtained without the use of propylene glycol.It is characteristic of my process that, when conditions are selectedsuch that the yield of raflinate oil obtained is greatly increased, theviscosity index is adversely affected only a very little, if at all. Notonly is the yield increased but the selectivity of the solvent atrelatively high extraction temperatures is also improved and a sharperseparation is obtained between the undesired naphthenic constituents ofthe oil and the desirable parailinic hydrocarbons.

The efl'ect of the addition of propylene glycol to chlor-ether may alsobe observed by referring to the accompanying drawing which forms a partof this specification. The graph shows the results of extracting amineral lubricating oil distillate of 60 S; A. E. viscosity rangederived from Salt Creek crude. It will be noted from the chart that fora given yield of rafllnate oil, the permissible temperature of operationis greatly increased by the addition of propylene glycol. Thus, at a 75%yield, chlor-ether requires a temperature of 112 F. whereas chlor-etherwith 8% propylene glycol requires a temperature of about 138 F., wellabove the melting point of this 'waxy oil. Likewise, 12% propyleneglycol permits a temperature of 158 F. with this same yield.

One of the advantages, of my process results from the fact thatthesolubility of propylene glycol in beta beta dichlor diethyl ether isvery small at low temperatures and therefore I may separate thepropylene glycol from the chlorether by cooling to 34 F. or lower, forexample, to 20 F. When water is present in the chlor ether solvent, itis not necessary to cool as low as this, and with chlor ether saturatedwith water, separation of propylene glycol (and water) occurs at about80 F. In this case, cooling below 80 F., for example to F., will resultin separation of the glycol.

On cooling two layers are formed, the upper layer consisting ofsubstantially pure propylene glycol. In carrying out my process I preferto analyze the solvent before use to determine the amount of propyleneglycol modifying agent which is present and then adjust theconcentration by adding to the solventsupply'the necessary amount ofeither chlor-ether or propylene glycol.

I may also initially extract a wax-containing oil at an elevatedtemperature above the melting point of the wax using between 10% and 30%of propyleneglycol in the solvent mixture. I may then cool the extractphase to a comparatively low temperature of the order of 50 1''. to: 90F. whereupon propylene glycol and a further quantity of oil or raflinateis caused to separate.

This second rainnate fraction maythen be further treated in the processor it may be disposed of as a second grade lubricating oil havingintermediate viscosity index.

Having thus described my invention, what I claim is:

1. The process of extracting undesirable constituents fromwax-containing mineral lubricating oils which comprises intimatelycontacting the oil with a solvent comprising beta beta dichlor diethylether and from 2-30% 'of propylene glycol, maintaining the temperatureof the conamass:

tactlng operation above the solidifying point of said wax-containinglubricating oil, separating said solvent and undesirable oilconstituents from the reflnedmineral lubricating oil and thereafterrecovering said solvent from said refined mineral oil and saidundesirable oil constituents.

2. In the process of extracting undesirable naphthenic constituents fromwax-containing mineral lubricating oils with beta beta dichlor diethylether, the improvement comprising incorporating in said ether 2-20% ofpropylene glycol and maintaining the temperature of said extractionoperation above the miscibility temperature of said ether and saidmineral oil but below the miscibility temperature of said mineral oiland said ether containing said propylene glycol.

3. In the process of: extracting undesirable naphthenic constituentsfrom mineral lubricating oils wherein the oil is intimately contactedwith beta beta dichlor diethyl ether and the undesirable constituentsare removed as an extract in solution in said ether, the improvementcomprising adding to said ether from 5 to 30% of propylene glycol,conducting the extraction at a temperature above the.solidifying pointof the oil, separating the oil-solvent mixture into a raffinate fractionand an extract fraction, cooling said extract fraction to a temperaturebelow 80 F. whereby said propylene glycol is caused to separate fromsaid extract fraction and separating and recovering said propyleneglycol for use, in further extraction-of additional quantities ofmineral lubricating oil.

4. In the process of extracting undesirable naphthenic constituents frommineral lubricating oils wherein the oil is intimately contacted with asolvent comprising beta beta dichlor di ethyl ether, the oil and solventmixture are permitted to separate into a raflinate fraction and anextract fraction, the raflinate fraction is sub iected to distillationto recover said solvent for reuse and produce a refined lubricating oil,andv 5. In the process of extracting lubricating oils' containingparaflin wax. with beta beta dichlor diethyl ether wherein the oil isintimately contacted with the ether and the oil and ether are separatedin two phases in which the heavier ether phase contains dissolvedundesirable naphthenic constituents of the oil, the improvementcomprising avoiding difllculties resulting from the separation of solidparaflin wax as a third phase in the process by adding between 5% and20% of propylene glycol to the beta beta dichlor diethyl ether wherebythe miscibility temperature of said ether and said lubricating oil israised substantially above the melting point of said waxy oil, andconducting the extraction at a temperature between the melting point ofsaid waxy oil and the said miscibility temperature,

- whereby said wax is prevented from crystallizing as a separate phasefrom said mixture.

' JAMES MORRIS PAGE, JR.

